Documentation translation (#199)

Documentation translation using weblate.

* Use po4a to generate .po files from the english markdowns, then to generate translated files
* Some pages can be marked as «english only» (for technical documentation for example)
* New Hugo shortcode to use application strings in documentation (for example for settings names)
* The code of conduct is no more translated, but there is a link to official Contributor Covenant translations
* Adding all plugin's supported languages

Related to https://github.com/JohnXLivingston/peertube-plugin-livechat/issues/117

support/documentation/content/en/contributing/document/_index.md

@@ -0,0 +1,98 @@
+---
+title: "Documentation"
+description: "Document the plugin, or translate the documentation."
+weight: 50
+chapter: false
+---
+
+## General information
+
+Always inform the community before working (by creating a new issue, or commenting an existing one).
+This is to avoid that two persons are working on the same thing, and prevent conflicts.
+
+Documentation work has to be merged in the `main` branch.
+
+The documentation source code is in the `support/documentation/content` folder.
+
+The documentation is generated using [Hugo](https://gohugo.io/).
+You have to install it on your computer if you want to preview your work.
+
+The used theme is [hugo-theme-learn](https://learn.netlify.app/).
+You should read its documentation before starting editing the documentation.
+
+When a new plugin version is released, or when documentation is updated, plugin maintainers will merge the `main` branch to the `documentation` branch.
+This will trigger github and gitlab pipelines, and update published documentation.
+
+## Translations
+
+The principal language is english (`en` code).
+
+The `support/documentation/content/en` folder contains only english documentation files.
+
+Documentation is translated using Weblate (see the [translation documentation](/peertube-plugin-livechat/contributing/translate/)).
+To do so, we use the [po4a tool](https://po4a.org/), as we will se later in this page.
+
+## Add a new language
+
+In the `support/documentation/config.toml` file, please copy and modify the `[Languages.fr]` section.
+
+If the translations are not complete, it does not matter, english will be used for missing strings.
+
+## Preview
+
+To preview your modifications, just run:
+
+```bash
+hugo serve -s support/documentation/
+```
+
+Then open your browser on the address [http://localhost:1313/peertube-plugin-livechat/](http://localhost:1313/peertube-plugin-livechat/).
+This page will automatically refresh on each modification.
+
+## Update localization files and generate documentation translations
+
+For now, you only have the english version.
+To update documentation strings, and generate translations, you have to run the `doc-translate.sh` script.
+
+To do so, make sure you have `po4a` (version >= 0.66) installed on your computer.
+
+{{% notice warning %}}
+Some linux distro (like Debian Bullseye for example) have too old version of `po4a`.
+Please make sure to install a compatible version.
+If you are using Debian Bullseye for example, you can download the Bookwork po4a.deb file from https://packages.debian.org, and install it manually.
+{{% /notice %}}
+
+To handle translations, just do:
+
+```bash
+npm run doc:translate
+```
+
+You can then preview the result using `hugo serve -s support/documentation/`, and using the language selector.
+
+## Write documentation
+
+Just edit the english files in `support/documentation/content/en`.
+
+Then, before commiting, always run `npm run doc:translate`, so that changes in english files can be propagated to the `support/documentation/po/livechat.en.pot` file.
+
+You can use the `livechat_label` short code to use application strings.
+See here: [Documentation translation](/peertube-plugin-livechat/contributing/translate/#documentation-translation).
+
+It is possible to prevent a file from beeing translating, using `livechatnotranslation: true` in the Yaml Font Matter section.
+See here: [Documentation translation](/peertube-plugin-livechat/contributing/translate/#documentation-translation).
+
+Please use the `livechatnotranslation` option for technical documentation.
+We don't want technical documentation to be translated, to avoid issues because of a wrong translation.
+
+Avoid adding line breaks in middle of a sentence.
+But add a line break after each sentence in a paragraph.
+This is to facilitate the work for translators: so then can easily check that they don't miss a sentence when translating a parapraph.
+
+### What if I can't use hugo and/or po4a?
+
+Just edit english markdown files, and specify that you can't build translations when you make your Pull Request.
+
+## Publication
+
+Publishing the documentation is automatic, as soon as the changes are merged into the `documentation` branch.